MAX5440
Stereo Volume Control with Rotary Encoder Interface
General Description
The MAX5440 dual, 40kΩ logarithmic taper volume control features a debounced up/down interface for use with a simple rotary encoder without using a microcontroller (μC). Each potentiometer has 32 log-spaced tap points with a buffered wiper output and replaces mechanical potentiometers. An integrated bias generator provides the required ((VDD + VSS)/2) bias voltage, eliminating the need for costly external op-amp circuits in unipolar audio applications. A mode-indicator LED output specifies volume or balance control. Five integrated LED drivers indicate volume level or balance settings, depending on the status of the mode indicator. The MAX5440 includes debounced pushbutton inputs for mute and mode. The mute input allows a single pushbutton to change between volume control and the -90dB (typ) mute setting. The mode input toggles between volume and balance control. A click-and-pop suppression feature minimizes the audible noise generated by wiper transitions. The MAX5440 provides a nominal temperature coefficient of 35ppm/°C end-toend and 5ppm/°C, ratiometrically. The MAX5440 is available in a 24-pin SSOP package and is specified for operation over the -40°C to +85°C extended temperature range.
Applications ●● ●● ●● ●●
Stereo Volume Control Desktop Speakers Multimedia Docking Stations Set-Top Boxes
Features ●● Logarithmic Taper Volume Control with (31) 2dB Steps ●● Low-Power Wiper Buffers Provide 0.003% THD ●● Single +2.7V to +5.5V or Dual ±2.7V Supply Voltage Operation ●● Low 0.5μA Shutdown Supply Current ●● Integrated Bias Voltage Generator ●● Five-Segment LED Volume/Balance Indicator ●● Clickless Switching ●● 40kΩ End-to-End Fixed Resistance Value ●● Mute Function Toggles to -90dB (typ) ●● Power-On Reset to -12dBFS Wiper Position
Ordering Information PART MAX5440EAG+
24 SSOP
Note: For leaded version, contact factory.
Typical Operating Circuit VLOGIC
VDD
VLOGIC SHDN
MODEIND
VPEAK (VDD + VSS) / 2
MAX5440
H1 W1
VLOGIC 1
24 GND
RENCODEB
2
23 MODEIND
RENCODEA
3
22 LEDIND4
RIGHT INPUT
L1
21 LEDIND3
MUTE
4 5
20 LEDIND2
SHDN
6
19 LEDIND1
LEDIND2
GND
7
18 LEDIND0
LEDIND3
H0
8
17 H1
L0
9
16 L1
MAX5440
H0
LEDIND4
BIAS
ROTARY ENCODER
RENCODEB
RENCODEA
13 VDD
VSS
W0
MODE
14 VSS
BIAS 12
L0
LEDIND1
MUTE
15 W1
LEDIND0
GND
W0 10 MIDBIAS 11
MIDBIAS
(VDD + VSS) / 2
MODE
SSOP
19-0542; Rev 3; 4/14
PIN-PACKAGE
+Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configuration TOP VIEW
TEMP RANGE -40°C to +85°C
LEFT INPUT
HEADPHONE DRIVER
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Absolute Maximum Ratings SHDN, MUTE, RENCODEA, RENCODEB, and MODE to GND...........................-0.3V to (VLOGIC + 0.3V) H_, L_, and W_ to VSS............................. -0.3V to (VDD + 0.3V) LEDIND_, MODEIND to GND..............-0.3V to (VLOGIC + 0.3V) MIDBIAS, BIAS to VSS.................. (VSS - 0.3V) to (VDD + 0.3V) VLOGIC to GND......................................... -0.3V to (VDD + 0.3V) VDD to GND.............................................................-0.3V to +6V VDD to VSS. .............................................................-0.3V to +6V
VSS to GND..............................................................-3V to +0.3V Input and Output Latchup Immunity................................±200mA Continuous Power Dissipation (TA = +70°C) 24-Pin SSOP (derate 12.3mW/°C above +70°C)......987.7mW Operating Temperature Range............................ -40°C to +85°C Junction Temperature.......................................................+150°C Storage Temperature Range............................. -60°C to +150°C Lead Temperature (soldering, 10s).................................. +300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Electrical Characteristics (VDD = +2.7V to +5.5V, VSS = VGND = 0, 2.7V ≤ (VDD - VSS) ≤ 5.5V, VLOGIC = +2.7V to VDD, VH_ = VDD, VL_ = VDD/2, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) PARAMETER End-to-End Resistance
SYMBOL
CONDITIONS
R
MIN 36
Absolute Tolerance Tap-to-Tap Tolerance
Total Harmonic Distortion Plus Noise
THD+N
TYP
MAX
UNITS
40
52
kΩ
±0.25
dB
±0.1
dB
VH_ = (VDD / 2) + 1VRMS, 1kHz tap at top, RL = J to VL_ = VDD / 2, 20Hz to 20kHz
0.004
VH_= (VDD / 2) + 1.5VRMS, 1kHz tap at top, RL = J to VL_ = VDD / 2, 20Hz to 20kHz
0.006
VDD = 5V,VSS = 0V, VL_ = 1.5V, VH_ = (VDD / 2) + 1VRMS, 1kHz tap at top, RL = 10kΩ to VMIDBIAS, 20Hz to 20kHz
0.004
VDD = 5V,VSS = 0V, VL_ = 5V, VH_ = (VDD / 2) + 1.5VRMS, 1kHz tap at top, RL = 10kΩ to VMIDBIAS, 20Hz to 20kHz
0.006
%
Channel Isolation
100
dB
Interchannel Matching
±0.5
dB
SHDN = VDD
90
dB
Input referred, 217Hz, 100mVP-P on VDD
-60
dB
5
pF
Mute Attenuation Power-Supply Rejection Ratio
PSRR
H Terminal Capacitance
CH
L Terminal Capacitance
CL
7
pF
End-to-End Resistance
35
ppm/°C
Ratiometric Resistance
5
ppm/°C
Bandwidth, -3dB Output Noise
fCUTOFF
CW = 33pF
100
kHz
en
20Hz to 20kHz
3.2
µVRMS
VO
RL = 10kΩ to VMIDBIAS
VDD - 0.2
V
WIPER BUFFER Output Voltage Swing Output Current Output Resistance
3 ROWB
DC Offset
-14
mA
1
10
Ω
±2
+14
mV
INTEGRATED BIAS GENERATOR Output Voltage
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ILOAD = 1mA
(VDD + (VDD + (VDD + VSS) / 2 VSS) VSS) / 2 - 30mV /2 + 30mV
V
Maxim Integrated │ 2
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Electrical Characteristics (continued) (VDD = +2.7V to +5.5V, VSS = VGND = 0, 2.7V ≤ (VDD - VSS) ≤ 5.5V, VLOGIC = +2.7V to VDD, VH_ = VDD, VL_ = VDD/2, TA = TMIN to TMAX, unless otherwise specified. Typical values are at TA = +25°C.) (Note 1) PARAMETER Power-Supply Rejection Ratio
SYMBOL PSRRBR
Maximum Load Output Resistance
CONDITIONS
MIN
1kHz, 100mV on VDD, 1µF on BIAS To VDD or GND
MAX
60
UNITS dB
3
kΩ
ROBR
6
Ω
RPULLUP
45
kΩ
CONTACT INPUTS (MUTE, MODE, RENCODEA, RENCODEB) Internal Pullup Resistor
TYP
Single Pulse Input Low Time
tCPW
Repetitive Input Pulse Separation
tIPWS
Timeout Period
tWS
Input High Voltage (Note 2)
VIH
Input Low Voltage (Note 2)
VIL
22 66 Click/pop suppression inactive
ms 32
DIGITAL INPUTS (MUTE, MODE, RENCODEA, RENCODEB, SHDN)
Input Leakage Current
ms
3.6V < VLOGIC ≤ 5.5V
2.4
2.7V ≤ VLOGIC ≤ 3.6V
2.0
ms
V
3.6V < VLOGIC ≤ 5.5V
0.8
2.7V ≤ VLOGIC ≤ 3.6V
0.6
Inputs unconnected
-1
Input Capacitance
+1 5
V µA pF
POWER SUPPLIES Supply Voltage
VDD
VSS = 0
2.7
5.5
V
Negative Power Supply
VSS
VDD = +2.7V
-2.7
0
V
Supply Voltage Difference Active Supply Current
VDD - VSS IDD
Standby Supply Current (Notes 3, 4)
ISTBY
Shutdown Supply Current
ISHDN
Power-Up Time Logic Supply Voltage Logic Active Supply Current
tPU VLOGIC IL
Logic Standby Supply Current
ILSTBY
Logic Shutdown Current
ILSHDN
Output Leakage Current Output Capacitance Maximum Sink Current
VOL
V
1.4
mA
VDD = +5V, VSS = 0
1.3
VDD = +2.7V, VSS = -2.7V
1.3
(Note 3)
1
Click/pop suppression inactive VSS = 0
50 2.7
VRENCODEA = VRENCODEB = 0V (Note 4)
LED INDICATORS (LEDIND0–LEDIND4, MODEIND) Output Low Voltage
5.5
µA ms
VDD
V
320
µA
1
µA
1
µA
VLOGIC = 2.7V, ISINK = 10mA
0.4
VLOGIC = 5.5V, ISINK = 10mA
0.2 0.1
mA
10
V µA
3
pF
150
mA
Note 1: Parameters are 100% production tested at +85°C and limits through temperature are guaranteed by design. Note 2: The device draws current in excess of the specified supply current when the digital inputs are driven with voltages between (VDD - 0.5V) and (GND + 0.5V). See Digital Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics. Note 3: Shutdown refers to the SHDN input being asserted low. Standby refers to SHDN not being asserted and all I/O inactive. Note 4: Supply current measured with the wiper position fixed.
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Maxim Integrated │ 3
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Typical Operating Characteristics (TA = +25°C, unless otherwise noted.)
-50 -60 -70
0
4
8
12
16
20
24
28
-0.10 -0.15 -0.20 -0.25
32
-40
100
-15
10
RENCODEB 51ms
WIPER TRANSITION FROM -2dB TO -4dB
1.42 1.41 1.40
60
1.38
85
-40
-15
VHW
70
0.8
60 50 40 30
VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
0.4 0 -0.8 -1.2 -1.6 -2.0
20
VWL
10
-2.4 -2.8
0
4
8
12
16
20
24
28
32
0.01
0.1
-6.8 -7.2
10
100
1000
THD+N vs. FREQUENCY 0.1
MAX5440 toc08
VDD = 2.5V VSS = -2.5V L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS
0.01
-7.6
1
FREQUENCY (kHz)
THD+N (%)
W_ SET TO -6dB
-6.4
THD+N (%)
RESPONSE (dB)
-6.0
85
W_ SET TO 0dB
-0.4
THD+N vs. FREQUENCY MAX5440 toc07
-5.6
60
FREQUENCY RESPONSE
FREQUENCY RESPONSE VH_ = 2.5 1VRMS, VL_ = 2.5V, CL_ = 33pF
35
WIPER-TO-END TERMINAL VOLTAGE vs. TAP POSITION
TAP POSITION
-5.2
10
TEMPERATURE (°C)
80
0.1
MAX5440 toc03
1.43
TEMPERATURE (°C)
90
0
20ms/div
35
RESPONSE (dB)
RENCODEA
NOMINAL END-TO-END VOLTAGE (%VHL)
MAX5440 toc04
1.44
1.39
TAP POSITION
WIPER SWITCHING TRANSIENT
1.45
MAX5440 toc06
-40
-0.05
1.46
W_ SET AT -6dB
VDD = 5.0V VSS = GND L_ = VMIDBIAS H_ = VMIDBIAS + 1VRMS
MAX5440 toc09
-30
0
VLOGIC = VDD = 5.5V
1.47 TOTAL SUPPLY CURRENT (mA)
-20
0.05
TOTAL SUPPLY CURRENT vs. TEMPERATURE
1.48
MAX5440 toc05
ATTENUATION (dB)
-10
0.10 END-TO-END RESISTANCE CHANGE (%)
MAX5440 toc01
0
END-TO-END RESISTANCE % CHANGE vs. TEMPERATURE MAX5440 toc02
ATTENUATION vs. TAP POSITION
W_ SET AT -6dB
0.01
W_ SET AT -2dB
-8.0
W_ SET AT -2dB
-8.4 -8.8 0.01
0.1
1
10
FREQUENCY (kHz)
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100
1000
0.001 0.001
W_ SET AT 0dB 0.01
0.1
1
FREQUENCY (kHz)
10
100
0.001 0.001
0.01
0.1
W_ SET AT 0dB 1
10
100
FREQUENCY (kHz)
Maxim Integrated │ 4
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.)
-45 -50 -55 -60 -65
150 100
0.1
1
10
50 0
100
SHUTDOWN 2.5
3.0
FREQUENCY (kHz)
4.0
4.5
5.0
200 150 100 50 0
-40
LOGIC SUPPLY VOLTAGE (V)
1.1766
-15
10
35
60
85
TEMPERATURE (°C)
DIGITAL SUPPLY CURRENT vs. DIGITAL INPUT VOLTAGE MAX5440 toc13
VDD = VLOGIC = 5.5V, RENCODEA = RENCODEB = 0
1.1768
RENCODEA = RENCODEB = 0
250
5.5
ACTIVE SUPPLY CURRENT vs. TEMPERATURE
1.1770
SUPPLY CURRENT (mA)
3.5
STANDBY CURRENT
VDD = VLOGIC = 5.5V,
300
1.1764 1.1762 1.1760 1.1758 1.1756
1000
MAX5440 toc14
0.01
MAX5440 toc11
200
-70 -75
ACTIVE CURRENT
ACTIVE LOGIC SUPPLY CURRENT vs. TEMPERATURE
350 LOGIC SUPPLY CURRENT (µA)
-40
250
DIGITAL SUPPLY CURRENT (µA)
RESPONSE (dB)
-35
LOGIC SUPPLY CURRENT (µA)
VDD_ = 5V 100mVP-P, VH = 5V VL_ = 2.5V, W_ SET TO -6dB
-30
300
MAX5440 toc10
-25
LOGIC SUPPLY CURRENT vs. LOGIC SUPPLY VOLTAGE
MAX5440 toc12
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
100
1.1754 -40
-15
10
35
60
DIGITAL INPUT VOLTAGE (V)
SPECTRAL NOISE DENSITY
SUPPLY CURRENT vs. INPUT VOLTAGE SWEEP 8
MAX5440 toc15
800 600 400 200
VDD = VLOGIC = 5V, W_ AT 0dB RL = 10kΩ TO VMIDBIAS
7 SUPPLY CURRENT (mA)
1000 NOISE (nV/√Hz)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
TEMPERATURE (°C)
1200
0
10
85
MAX5440 toc16
1.1752
6 5 4 3 2 1
0.01
0.1
1 FREQUENCY (kHz)
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10
100
0
2.5
3.0
3.5
4.0
4.5
5.0
INPUT VOLTAGE SWEEP (VH_)
Maxim Integrated │ 5
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Pin Description PIN
NAME
1
VLOGIC
2
RENCODEB
Rotary Encoder Input B. With RENCODEA, this input provides the rotary encoder control for the potentiometer (see Figure 1). RENCODEB is internally pulled up to VLOGIC with a 45kΩ resistor.
3
RENCODEA
Rotary Encoder Input A. With RENCODEB, this input provides the rotary encoder control for the potentiometer (see Figure 1). RENCODEA is internally pulled up to VLOGIC with a 45kΩ resistor.
4
MUTE
Mute Input. Pull MUTE low to toggle the wiper between the mute setting (see Table 1) and the current setting. MUTE is pulled up to VLOGIC with an internal 45kΩ resistor.
5
MODE
Volume/Balance Control Input. Each high-to-low transition on MODE toggles between the volume and balance modes. MODE is pulled high internally with a 45kΩ resistor to VLOGIC. On power-up, the MAX5440 is in volume-control mode.
6
SHDN
Active-Low Shutdown Input. Drive SHDN low to place the device in shutdown mode. In shutdown mode, the MAX5440 stores the last wipers settings. The wipers move to the L_ end of the resistor string. Terminating shutdown mode restores the wipers to their previous settings.
7, 24
GND
8
H0
Potentiometer 0 High Terminal. H0 and L0 terminals can be reversed.
9
L0
Potentiometer 0 Low Terminal. L0 and H0 terminals can be reversed.
10
W0
Potentiometer 0 Wiper Buffered Output
11
MIDBIAS
12
BIAS
Bias Generator Input. Bypass with a 1µF capacitor to system ground.
13
VDD
Analog Power Supply. Bypass VDD to ground with a 0.1µF capacitor as close to the device as possible.
14
VSS
Negative Power Supply. Bypass VSS to ground with a 0.1µF capacitor as close to the device as possible. Connect to GND for single-supply operation.
15
W1
Potentiometer 1 Wiper Buffered Output
16
L1
Potentiometer 1 Low Terminal. L1 and H1 terminals can be reversed.
17
H1
Potentiometer 1 High Terminal. H1 and L1 terminals can be reversed.
18–22
LEDIND0– LEDIND4
LED Indicator Open-Drain Output 0 through LED Indicator Open-Drain Output 4. LEDIND0–LEDIND4 form a bar graph indication of the current volume or balance. In volume mode, all LEDs off indicates mute and all LEDs on indicates maximum volume. In balanced mode, LED2 on indicates centered or balanced.
23
MODEIND
Volume-Control/Balance-Control Mode Indicator Open-Drain Output. Connect to an LED through a resistor to VLOGIC. When the LED is on, the MAX5440 is in balance-control mode. When the LED is off, the MAX5440 is in volume-control mode.
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FUNCTION Digital Logic Power Supply. Bypass VLOGIC to ground with a 0.1µF capacitor as close to the device as possible.
Ground. Connect pins 7 and 24 together.
Midbias Voltage Output. VMIDBIAS = (VDD + VSS) / 2.
Maxim Integrated │ 6
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Detailed Description
Rotary Encoder Interface
The MAX5440 dual, 40kΩ logarithmic taper digital potentiometer features a debounced up/down interface for use with a simple rotary encoder without using a microcontroller. Each potentiometer has 32 log-spaced tap points with a buffered wiper output and replaces mechanical potentiometers.
The MAX5440 interfaces with rotary encoder switches. The rotary encoder is a contact closure type switch with two outputs that connect to RENCODEA and RENCODEB on the device. As the shaft is rotated, RENCODEA and RENCODEB produce a gray code count. Figure 1 shows a typical rotary encoder interface.
Mode Control (MODE)
State changes trigger a wiper movement and the direction of the count dictates the direction of wiper movement. An increasing gray code count moves the wiper up to a lower attenuation setting in volume mode and towards a full right channel (CH1) in balance mode. A decreasing gray code count moves the wiper down to a higher attenuation in volume mode and towards a full left channel (CH0) in balance mode. Both switch inputs are internally pulled up to VLOGIC by internal 45kΩ resistors.
The MAX5440 MODE input toggles between volume and balance modes. Force MODE low to toggle between volume and balance modes. For example, driving MODE low once while in volume-control mode switches the MAX5440 to balance mode. Driving MODE low again switches the MAX5440 back to volume mode. MODE is internally pulled high with a 45kΩ resistor to VLOGIC. The MAX5440 powers up in volume-control mode. Leave unconnected or connect to VLOGIC if balance mode is not required.
During rapid rotation, the inputs must be stable for at least 20ms and have separation between state changes by at least 40ms for the debounce circuitry to accurately detect the input states.
VLOGIC 1/4 CYCLE PER DETENT CW 45kΩ
45kΩ
RENCODEA
A
RENCODEB
B
CHANNEL A
OPEN CIRCUIT CLOSED CIRCUIT OPEN CIRCUIT CLOSED CIRCUIT
MAX5440
ROTARY ENCODER
D
GND
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
CHANNEL B
CLOCKWISE ROTATION INCREASING GRAY CODE (AB)
11, 10, 00, 01, 11, 10, ETC.
COUNTERCLOCKWISE ROTATION DECREASING GRAY CODE (AB)
11, 01, 00, 10, 11, 01, ETC.
Figure 1. Rotary Encoder Interface
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Maxim Integrated │ 7
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Volume Control
In volume-control mode, the MAX5440’s wipers move simultaneously, maintaining the balance separation between each wiper (Figure 2a). When either wiper reaches the maximum tap position (position closest to H_), further commands to increase the volume are ignored. Balance separation is maintained in the maximum volume configuration (Figure 2b). When either wiper reaches the minimum tap position (position closest to L_), further commands to decrease
the volume adjust the other wiper until it also reaches the minimum tap position (Figure 2c). Increasing the volume from this minimum position restores the original balance separation of the wipers (Figure 2d). When both wipers are in the tap 31 position (-62dB attenuation), further decreasing rotations place the wipers in the mute position (see Table 1). Rotating the encoder to a lower attenuation or a pulse to MUTE returns the wipers to tap 31.
BALANCE SEPARATION MAINTAINED W0 W1
H_ W0
W1
W1
W0 ROTATE CW TWICE
ROTATE CCW ONCE
L_
H_
a
W0
W1
W0
W1
ROTATE CW ONCE
NO CHANGE
W1
ROTATE CW
L_
H_
W0
b
W0
W1
W0
W1
ROTATE CCW ONCE
W0
W1
ROTATE CCW
TO D
L_ c
ORIGINAL BALANCE SEPARATION MAINTAINED W0 W1
H_ W0
W1
W0
W1
ROTATE CW ONCE
FROM C
ROTATE CW ONCE
L_ d
Figure 2. Volume-Control Operation
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Maxim Integrated │ 8
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Table 1. Wiper Position and Attenuation POSITION
Balance Control
In balance-control mode, the MAX5440 adjusts the balance between channel 0 and channel 1 while maintaining the set volume. For example, if the volume of channel 0 equals the volume of channel 1, forcing the balance towards channel 1 increases the attenuation of channel 0 (Figure 3a). If channel 1 is at a higher attenuation than channel 0, adjusting the balance to channel 1 moves channel 1’s wiper up to the same wiper position as channel 0 before it was attenuated (Figure 3b).
ATTENUATION (dB)
0
0
1
-2
2
-4
…
…
6 (POR)
-12
…
…
30
-60
31
-62
32 (MUTE)
≥ 90
Click-and-Pop Suppression
The click-and-pop suppression feature reduces the audible noise (clicks and pops) that results from wiper transitions. The MAX5440 minimizes this noise by allowing the wiper to change position only when VH = VL. Each wiper has its own suppression and timeout circuitry. The MAX5440 changes wiper position when VH = VL, or after 32ms, whichever occurs first (see Figures 4a and 4b). The suppression circuitry monitors left and right channels separately. In volume-control mode, when the first wiper changes position, the second wiper has 32ms to change or it will be forced to change.
VOLUME LEVEL IS SET
VOLUME LEVEL MAINTAINED BALANCE SHIFTS TO W1
H_ W0
W1
W0
W1
W0
W1
ROTATE CW ONCE
ROTATE CW ONCE
L_ VOLUME LEVEL MAINTAINED BALANCE SHIFTS TO W1
VOLUME LEVEL IS SET BY W0 H_ W0
W1
W0 ROTATE CW ONCE
W1
W0
W1
ROTATE CW ONCE
L_
Figure 3. Balance-Control Operation
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Maxim Integrated │ 9
MAX5440
Stereo Volume Control with Rotary Encoder Interface
USER ROTATES ENCODER SWITCH CONTACT IS BOUNCING
01
SWITCH CONTACT IS STABLE
SWITCH CONTACT IS BOUNCING
INPUT ACCEPTED
00 tWS
tHPW
WAIT FOR FIRST ZERO CROSSING, tWS
DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW
tLPW DEBOUNCE BY WAITING FOR STABLE LOW, tLPW
VH_
VL_
WIPER MOVES HERE
2dB STEPS WIPER MOTION
Figure 4a. Wiper Transition Timing Diagram—Suppression Circuitry Active
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Maxim Integrated │ 10
MAX5440
Stereo Volume Control with Rotary Encoder Interface
SWITCH CONTACT IS STABLE
SWITCH CONTACT IS BOUNCING
SWITCH CONTACT IS BOUNCING
01 READY TO ACCEPT ANOTHER ENCODER INPUT SIGNAL INPUT ACCEPTED
00 tWS
tHPW
WAIT FOR FIRST ZERO CROSSING OR TIMEOUT, tWS
tLPW
DEBOUNCE BY WAITING FOR STABLE HIGH, tHPW
DEBOUNCE BY WAITING FOR STABLE LOW, tLPW
VH
VL
WIPER MOVES HERE
(tLPW + tWS) 2dB STEPS
Figure 4b. Wiper Transition Timing Diagram—Timed Out
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Maxim Integrated │ 11
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Power-On Reset
The power-on comparators monitor (VDD - VSS) and (VLOGIC - GND). A power-on reset is initiated when either of the supplies is brought back to the normal operating voltage. The power-on reset feature sets both wipers to -12dB. The wipers initially wake up in mute mode (-90dB) and move to the -12dB position when VH = VL to eliminate clicks and pops during power-up. With DC inputs at VH and VL, the wipers move after exceeding the timeout period. A power-on reset places the MAX5440 in volumecontrol mode.
Shutdown (SHDN)
Upon entering shutdown, the MAX5440 stores the last wiper settings. The wipers move to the L_ end of the resistor string. The wipers move to the L_ end of the resistor string when VH = VL to eliminate clicks and pops during shutdown. With DC inputs at VH and VL, the wipers move after exceeding the timeout period. Exiting shutdown restores the wipers to their previous settings.
Mute Function (MUTE)
The MAX5440 features a mute function input, MUTE. Successive low pulses on MUTE toggle its setting. Activating the mute function forces both wipers to maximum attenuation (-90dB typ). Deactivating the mute function returns the wipers to their previous settings. Rotating the encoder clockwise (increasing gray code count) also deactivates mute, setting the wipers to their previous positions. MUTE is internally pulled high with a 45kΩ resistor to VLOGIC. When both wipers are in the tap 31 position (-62dB attenuation) further commands to lower the volume (decreasing gray code count) place the wipers in the mute position (see Table 1). Rotating the encoder to a lower attenuation or a pulse to MUTE returns the wipers to tap 31.
Mode Indicator (MODEIND)
The open-drain MODEIND indicates volume-control mode or balance-control mode for the MAX5440. Connect MODEIND to an LED with a series resistor to VLOGIC. When the LED is on, the MAX5440 is in balancecontrol mode. When the LED is off, the MAX5440 is in volumecontrol mode. See the Mode Control (MODE) section for more detail on switching between modes.
Level Indicator LEDs
The MAX5440 includes five indicator LED drivers to display the current wiper settings in either volume or balance mode. Connect the LEDIND_ outputs to the LEDs and to VLOGIC through a series resistor as shown in the typical application circuits. In volume-control mode, all LEDs are off when the wipers reach the highest attenuation levels (mute). All LEDs are on at the lowest attenuation levels (0dB). Table 2 shows the LED display as the wipers transition through various attenuation levels. In balance-control mode, only one LED is on at a time to indicate the current balance setting. Figure 5 shows the LEDs display for the current balance setting. When LED2 is on, the display indicates that the channels are centered or balanced at a set volume level. Turning the encoder clockwise (an increasing gray code count) turns LED3 on to represent a balance shift towards channel 1. When LED4 turns on, the balance shifts completely toward channel 1 and channel 0 is fully attenuated. From a balanced position, turning the encoder counterclockwise (a decreasing gray code count) turns on LED1, and then LED0 to indicate a balance shift towards channel 0.
Table 2. LED Settings in Volume Mode VOLUME POSITION (dB)
VOLUME LED OUTPUTS (1 = LED IS ON) LED0
LED1
LED2
LED3
LED4
0 to -8
1
1
1
1
1
-10 to -18
1
1
1
1
0
-20 to -28
1
1
1
0
0
-30 to -38
1
1
0
0
0
-40 to -52
1
0
0
0
0
-54 to mute (-90)
0
0
0
0
0
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Maxim Integrated │ 12
MAX5440
Stereo Volume Control with Rotary Encoder Interface
FULL L
L + 12
L+6
R+6
CCW ROTATION (CH0) LED0 ON
R + 12 CW ROTATION (CH1)
CENTERED
LED1 ON
FULL R
LED2 ON
LED3 ON
LED4 ON
Figure 5. LED Setting in Balance Mode
VDD
VLOGIC
VLOGIC SHDN
MODEIND VPEAK
MAX5440
0V
H1 W1 RIGHT INPUT
L1
(VDD + VSS) / 2
HEADPHONE DRIVER
MIDBIAS
LEDIND0
L0
LEFT INPUT
LEDIND1
W0
LEDIND2 LEDIND3
H0
LEDIND4
BIAS
RENCODEB
RENCODEA
MODE
MUTE
GND
VSS = -VDD
ROTARY ENCODER
Figure 6. Dual-Supply Volume/Balance Control
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MAX5440
Multiple Button Pushes (MODE, MUTE)
The MAX5440 does not respond to simultaneous button pushes. Pushing more than one button at the same time stops the wipers in their present states. Only a single button push configures the device.
Stereo Volume Control with Rotary Encoder Interface Chip Information PROCESS: BiCMOS
Applications Information Typical Application Circuit
The Typical Operating Circuit shows the MAX5440 in a typical volume/balance application using a single-supply configuration. Figure 6 shows a typical volume/balance application circuit using the MAX5440 in a dual-supply configuration. The MAX5440 does not require external op amps because the bias is generated internally, and the wipers have internal low-power buffers for low distortion. Connect the W_ outputs of the MAX5440 to the left and right inputs of a stereo audio amplifier, such as the MAX9761. The rotary encoder controls the potentiometer attenuation levels without using a microcontroller. Use the MODE input to switch between volume-control and balance-control modes.
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Maxim Integrated │ 14
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Revision History VLOGIC
SHDN
VDD
BIAS
MODEIND
VSS
MIDBIAS
LEDIND0
LEDIND1
LEDIND2
LEDIND3
LEDIND4
BIAS GENERATOR
MAX5440
H1
H0 CLICK-AND-POP SUPPRESSION CIRCUITRY
0
CLICK-AND-POP SUPPRESSION CIRCUITRY
0
1
1
2
2
3
3
POSITION COUNTER
4
POSITION COUNTER
4
W0
W1 UP/DOWN
UP/DOWN
28
28
TIMING AND CONTROL
29
29
30
30 DEBOUNCE
DEBOUNCE
DEBOUNCE
DEBOUNCE
31
VLOGIC
45kΩ
45kΩ
45kΩ
31
45kΩ MUTE
MUTE
L0
DEBOUNCE
GND
RENCODEA
RENCODEB
MODE
L1
MUTE
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
24 SSOP
A24-1
21-0056
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Maxim Integrated │ 15
MAX5440
Stereo Volume Control with Rotary Encoder Interface
Revision History REVISION NUMBER
REVISION DATE
PAGES CHANGED
2
11/08
Fixed pin names and thermal data. Updated two specifications in EC table
3
4/14
Updated Applications
DESCRIPTION
1, 2, 3, 6, 13 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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